Microtreatment of iron-based alloy, apparatus and method therefor and articles resulting therefrom

ABSTRACT

Iron-based alloys and articles in strips, sheets, workpieces and the like are converted into high strength steel with a minimum of cost, time and effort, including producing dual phase materials. This is achievable by extremely rapid micro-treating of low, medium, and high carbon iron-based alloys and articles by rapid heating and rapid cooling at least a portion of the alloy/article. This heating step involves nearly immediately heating the iron-based alloy to a selected temperature above its austenite conversion temperature. Then, the alloy is immediately quenched, also at an extremely fast rate, on at least a portion of the iron-based alloy in a quenching unit adjacent the heating unit. This procedure forms high strength alloy in a desired area, depending upon where the treatment was performed.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of nine (9) U.S. ProvisionalApplications Nos. 60/827,929, 60/862,302, 60/886,826, 60/889,197,60/889,221, 60/895,773, 60/917,551, 60/942,078, 60/953,841 filed on Oct.3, 2006, Oct. 20, 2006, Jan. 27, 2007, Feb. 9, 2007, Feb. 9, 2007, Mar.20, 2007, May 11, 2007, Jun. 5, 2007, and Aug. 3, 2007, respectively,which are incorporated herein by reference.

TECHNICAL FIELD

These inventions relate to treated iron-based alloys, and moreparticularly relate to processes and apparatuses for transforming lowquality ferrous alloys into high strength steel.

BACKGROUND OF THE INVENTION

Traditionally, metallurgists have wanted to take low quality metals,such as ferrous alloys and low carbon steel, and turn them into highquality steels and more desirable products through inexpensivetreatments, including annealing, quenching, and tempering to name a few.Previous attempts have met with limited success in that they did notalways produce a desirable product. Other attempts have failed on alarge scale due to high processing costs.

Processing of high strength steel generally takes heavy capitalequipment expenditures, expensive and dangerous heated fluids, such asquenching oils and quenching salts, and tempering/annealing processeswhich include the use of ovens, heating equipment, and residual heatfrom pouring molten steel. These quenching procedures are intended toraise the hardness of the steel to a desirable value. Bainite andmartensite are two high strength phases of steel that can be made bythese processes and are very desirable materials for certain highstrength applications as they generally have Rockwell C hardness of fromabout 30 and up. The increased hardness correlates to a comparableincrease in tensile strength. From widely published charts, it isaccepted that a low carbon steel with a Rockwell C hardness of 31 has atensile strength of about 1005 MPa.

Typical advanced high strength steels include such bainitic and/ormartensitic phases. Bainite is generally an acicular steel phasestructured of a combination of ferrite and carbide that exhibitsconsiderable toughness with high ductility. Usually formed byaustempering, the bainite phase is a very desirable product. Onepractical advantage of bainitic steels is that relatively high strengthlevels can be obtained together with adequate ductility without furtherheat treatment, after the bainite reaction has taken place. Such steels,when made as a low carbon alloy, are readily weldable, and bainite willform in the heat-affected zone adjacent to the weld metal, therebyreducing the incidence of cracking. Furthermore, these steels having alower carbon content tend to improve the weldability and reduce stressesarising from transformation. When traditional bainite is formed inmedium and high carbon steels, weldability is reduced due to the highercarbon content. However, industry would find a great benefit in a highstrength steel that is weldable.

The other conventional high strength steel, martensite, is anotheracicular steel phase made of a hard, supersaturated solid solution ofcarbon in a body-centered tetragonal lattice of iron. It is generally ametastable transitional structure formed during a phase transformationcalled a martensitic transformation or shear transformation in whichlarger workpieces of austenized steel may be quenched to a temperaturewithin the martensite transformation range and held isothermally at thattemperature to attain an equalized temperature throughout before coolingto room temperature. In thinner sections, martensite is often quenchedin water.

Since chemical processes accelerate at higher temperatures, the strengthassociated with martensite is easily tempered/destroyed by theapplication of heat. In some alloys, this effect is reduced by addingelements such as tungsten that interfere with cementite nucleation, but,more often than not, the phenomenon is exploited instead. Sincequenching can be difficult to control, most steels are quenched toproduce an overabundance of martensite, and then tempered to graduallyreduce its concentration until the right structure for the intendedapplication is achieved. Too much martensite leaves steel brittle,whereas too little martensite leaves it soft.

It is a first aspect of the present invention to provide an inexpensive,quick and easy way to produce a low, medium, or high carbon iron-basedalloy containing a high percentage of high strength steel while havingsome of the desirable mechanical properties of traditional bainiteand/or martensite.

It is a second aspect of the present invention to provide a method andapparatus for micro-treating low, medium, or high carbon iron-basedalloys to contain a desirable quantity of a new microstructure,including coalesced bainite, bainite and/or martensite or bainiteitself, martensite itself, ferrite, pearlite, or combinations of thevarious materials thereof. The micro-treated low, medium, or high carboniron-based alloy may have varying thicknesses for different applicationsand may be readily weldable while having high tensile strength, alongwith the ability to save material and reduce weight.

SUMMARY OF THE INVENTION

In accordance with the present invention, low grade ferrous alloys instrips, sheets, bars, plates, tubes, workpieces and the like areconverted into high strength steel with a minimum of cost, time andeffort. Dual and multiple phase materials are achievable by practicingthe present invention.

Following the practices of the present invention, a new microstructurewhich this patent shall refer to as “Colascite”, is made by treatingiron-based ferrous alloys including low, medium, and high carbon steeland other iron-based alloys to this new steel microstructure. Therefore,the term “Colascite”, shall hereinafter refer to the microstructurewhich may include portions of coalesced bainite, bainite, acicularferrite, retained austenite, pearlite, ferrite and/or martensite andcombinations thereof by micro-treating the iron based alloy.

Upon testing by several of the world's leading metallurgists, there isdebate as to which of many known microstructures Colascite may mostclosely resemble. Therefore, the term “Colascite” will be incorporatedthrough the remainder of this application to describe the individualmicrostructure, or combinations of those aforementioned, transformed inaccordance with the present invention. The characteristics of“Colascite” will be described in more detail further hereinbelow withreference to photomicrographs depicting the new microstructure.Transmission electron microscopy, orientation image microscopy, and atomfield ion probe microscopy have shown unique arrangements when comparedto conventional microstructures. To the best knowledge of the inventor,some of the alloys tested resulted in distortion free presumed bodycentered cubic structure, while others displayed body centeredtetragonal with limited distortion.

While commercially available ultra/advanced high strength steels havetensile strengths ranging up to 1400 Mpa, elongation of such steelstends to be at only 3%. In common use, many steels only have 800-1000Mpa tensile strength but more elongation, ranging up to 10%. Elongationmost often comes at a sacrifice in strength. In many cases these steelscan only achieve their strength with the addition of increased carboncontent, extensive alloying, and/or hot or cold working, including, butnot limited to, continuous annealing. In order to make the 1400 Mpa/3%elongation steel example above, it is generally required to performsignificant, cold working, martensitic transformation, subsequenttempering along with having, a carbon level of 0.18% wt to achieve suchmechanical properties. The addition of carbon is usually detrimental towelding characteristics, so manufacturers prefer to see carbon levels of0.13% wt. or less.

It is a desirable aspect of the present invention to provide a highstrength steel that combines significantly high tensile strength withfar superior elongation. Steels with 0.13% wt or less of carbon and verylow alloy content transformed to Colascite using the described methodshave exhibited more than 1400 Mpa average tensile strength exhibiting upto 7.6% elongation, with an average elongation of 6.5%. Other Colascitesteels made from AISI8620, have exhibited tensile strengths from 1500 to1650 Mpa exhibiting with 5.5 to 7.6% elongation. This elongation is morethan 2.5 times greater than the elongation of comparable strengthmartensitic steel. AISI4130, another common commercial steel,transformed to Colascite, has 1850 Mpa tensile strength exhibiting anaverage elongation of over 6%, which is more than 3 times greater thanthe elongation of other 0.30% wt carbon steels that have a comparablehigh strength microstructure.

There are provided methods and apparatuses for extremely rapidmicro-treating of low, medium, and high carbon iron-based alloys andarticles made from and containing those alloys. The iron-based, orferrous, alloys/articles start out having a first microstructure priorto the micro-treating, and are converted into a second microstructure byrapid heating and rapid cooling into high strength steels on at least aportion of the alloy/article. All ultralight metals, including aluminum,copper and magnesium exhibit a change in grain size and mechanicalproperties when microtreated under this process. It is expected that anymetal will change its microstructure and mechanical properties to acertain extent when processed.

A method for rapidly micro-treating an iron-based alloy is disclosed forforming at least one phase of a high strength alloy, where the methodcomprises the steps of providing an iron-based alloy having a firstmicro-structure with an austenite conversion temperature. This firstmicrostructure is capable of being transformed to an iron-based alloyhaving a second micro-structure including the above mentioned phases byrapidly heating at an extremely high rate, such as 315° C./sec to 3000 °C./sec.

This heating step involves nearly immediate heating of the iron-basedalloy to a selected temperature above its austenite conversiontemperature. Then, the alloy is immediately quenched, also at anextremely fast rate, i.e. 315° C./sec to 6,000° C./sec on at least aportion of the iron-based alloy in a quenching unit adjacent the heatingunit. This procedure forms at least one phase of a high strength alloyin a desired area, depending upon where the treatment was performed.Extremely rapid quenching will form at least one phase of a highstrength alloy, as described more fully hereinbelow.

Quenching may be accomplished nearly instantaneously by various methodsand apparatuses, including water baths, water sprays, chilled formingdies, air knives, open air convection, final operation chilledprogressive dies, final stage chilled line dies, chilled roll formingdies, and quenching hydroforms among others.

In various aspects of the apparatus portions of the invention, variousheating units are used, including stationary, hinged, and movable headheating units. These various types of heating units have found utilityfor the method, where the movable and hinged head heating units werehelpful for following contours on workpieces having a non-planarconfiguration during the rapid heating step for heating the low carboniron-based alloy to its desired selected elevated temperature. Computercontrol units help to move the heating units responsive to the surfaceconfiguration of the workpiece. In addition to the heating and quenchingunits, spaced first and second tensioning units may be positioned onopposite sides of the heating and quenching units for moving theiron-based alloy article through the heating and quenching units.

The resulting high strength steel may include at least one portion ofthe resulting high strength material made of Colascite, coalescedbainite, martensite, ferrite, austenite, pearlite, and/or dual phasecombinations thereof, depending on the placement of the treatmentsdescribed and claimed hereinbelow.

Dual phase materials can be made, such as a martensitic phase locatednext to a Colascite phase, or a ferritic phase in combination with aColascitic phase. These highly desired dual phase materials areachievable in the same workpiece by quenching only in various patternsso that a pattern of high strength steel can be manufactured in desiredareas across the surface and/or cross section of an article after it hasbeen heated. By only quenching certain areas, various material phasesare possible in various locations where desired.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and advantages of the expectedscope and various embodiments of the present invention, reference shallbe made to the following detailed description, and shall be taken inconjunction with the accompanying drawings, in which like parts aregiven the same reference numerals, and wherein:

FIG. 1 is a flowchart of a process of making a Colascite article inaccordance with the present invention;

FIG. 2a is a temperature vs. time diagram illustrating the change oftemperature during the heating and quenching steps for processing aspecimen of ferrous alloy;

FIG. 2b is a second temperature vs. time diagram illustrating the changeof temperature during the heating and quenching steps for processing aspecimen of ferrous alloy;

FIG. 3 shows a workpiece of ferrous alloy;

FIG. 4 is a view of an apparatus for processing a ferrous alloy inaccordance with the present invention;

FIGS. 5A and 5B show various embodiments of a side-to-side movableheater in accordance with the present invention;

FIGS. 6A and 6B show a vertically oriented movable heater in accordancewith the present invention;

FIG. 7 shows still another embodiment of the movable heater of thepresent invention;

FIG. 8 shows a hinged movable heater in accordance with the presentinvention;

FIG. 9 is a flowchart of a process of making a Colascite article inaccordance with the first embodiment of the present invention;

FIG. 10 is a temperature vs. time diagram illustrating the change oftemperature during the heating and quenching steps for processing aspecimen of ferrous alloy in accordance with the first embodiment;

FIG. 11 shows a workpiece of ferrous alloy;

FIG. 12 is a view of an apparatus for heating and stamping a ferrousalloy in accordance with the first embodiment of the present invention;

FIG. 13 is a flowchart of a process of making a Colascite near netshaped article in accordance with the second embodiment of the presentinvention;

FIG. 14 is a temperature vs. time diagram illustrating the change oftemperature during the heating and optional quenching steps forprocessing a specimen of Colascite ferrous alloy in accordance with thesecond embodiment;

FIG. 15 shows a workpiece of Colascite ferrous alloy;

FIG. 16 is a view of an apparatus for heating and stamping a Colasciteferrous alloy in accordance with the second embodiment of the presentinvention;

FIG. 17 is a view of an apparatus for heating and progressive diestamping a Colascite ferrous alloy in accordance with the secondembodiment of the present invention;

FIG. 18 is a view of an apparatus for heating and line die stamping aColascite ferrous alloy in accordance with the second embodiment of thepresent invention;

FIG. 19 is a view of an apparatus for heating and roll forming aColascite ferrous alloy in accordance with the second embodiment of thepresent invention;

FIG. 20 is a view of an apparatus for heating and self containedconventional forming of a Colascite ferrous alloy in accordance with thesecond embodiment of the present invention;

FIG. 21 is a view of an apparatus for heating and expansion hydroforminga Colascite ferrous alloy in accordance with the second embodiment ofthe present invention;

FIG. 22 is a view of an apparatus for heating and bladder hydroforming aColascite ferrous alloy in accordance with the second embodiment of thepresent invention;

FIG. 23 is a view of an apparatus for heating and liquid punchhydroforming a Colascite ferrous alloy in accordance with the first andsecond embodiments of the present invention;

FIG. 24 is a flowchart of a process of making a Colascite article inaccordance with the third embodiment of the present invention;

FIG. 25 is a temperature vs. time diagram illustrating the change oftemperature during the heating and quenching steps for processing aspecimen of ferrous alloy in accordance with the third embodiment;

FIG. 26 is a view of an apparatus for local environment heating andpressure forming a Colascite ferrous alloy in accordance with the fourthembodiment of this invention. The second and third embodiments of thepresent invention are incorporated by reference;

FIG. 27 is a photomicrograph of the material made in accordance with thepresent invention;

FIG. 28 is a photomicrograph showing an identical precursor to FIG. 27,although it is austempered in molten salt to produce much larger grains;

FIG. 29 is a photomicrograph of an austempered alloy quenched withmolten salt;

FIG. 30 is a side perspective view of a hollow tube being microtreated;

FIG. 31 illustrates an automotive hood being micro-treated from only oneside of the ferrous workpiece;

FIG. 32 is an automotive hood outer being roller hemmed over the hoodinner in accordance with the second and third embodiments of the presentinvention;

FIG. 33 shows a side elevational view of a repeating heat and quenchsequence obtained by a multiplicity of heat/quench apparatus; and

FIG. 34 is a side elevational view of a convoluted configuration beingsubjected to movable heat and quench units which may run the path ofmotion multiple times to treat a given workpiece.

DETAILED DESCRIPTION OF THE INVENTION

The present invention discloses a method of making controllable highpercentage high strength steels including Colascite, coalesced bainite,bainite, martensite, austenite, acicular ferrite, retained ferrite,pearlite and combinations thereof in ferrous alloys and severalapparatuses of making the same. As shown in FIG. 1, the process ofmaking Colascite in a ferrous alloy includes providing a ferrous alloyworkpiece 11, extremely rapidly heating of the workpiece at least abovethe austenite conversion temperature 12 and then immediately quenchingthe workpiece to a sub-austenitic temperature, preferably ambient,within an extremely short period 13. In one aspect of the invention,this extremely rapid heating and immediate quenching can be performedentirely within less than a second, but may take several to manyseconds. The transformed ferrous alloy workpiece 14 may have a preferredmicrostructure, comprising at least localized portions, of saidworkpiece that are made from about 5% to 100% Colascite. A transformedworkpiece may be almost fully transformed to Colascite. Various factors,such as mechanical stresses, austenizing temperature, prior processing,the starting microstructure, and/or composition of the ferrous alloysbeing treated may affect the transformation of these high strengthmaterials, along with the resulting grain size, and may further resultin different concentrations of Colascite. To achieve yet another aspectof the present invention, an additional step of tempering or annealingmay be optionally included to relieve stresses and prevent cracking ofthe resulting workpiece.

The process of the present invention may apply to various ferrousalloys. It is feasible to utilize the present invention on ferrousalloys in the form of strips, wires, sheets, plates, workpieces indifferent shapes, or hollow tubes, which can be used for flagpoles andbar stock as well. The method of making high strength material of thepresent invention may also apply to net shaped, or near-net shapedarticles made of ferrous alloys. One useful ferrous alloy may containcarbon in the range of from about 0.001 percent carbon by weight (wt %)to about 4 percent carbon by weight (wt %). Another useful ferrous alloymay contain carbon in the range of 0.003 percent carbon by weight (wt %)to 2 percent carbon by weight (wt %). Yet another useful composition hasa carbon content from about 0.1 wt % to about 0.7 wt %. In fact, a pieceof AISI18620 converted to Colascite by heating to 1065° C. andimmediately quenching in water yielded grain size of 5 to 7, elongationof 5-8%, strength 235 Ksi.

FIG. 2 is a temperature vs. time diagram illustrating the change oftemperature during the heating and quenching steps for one aspect of theinvention for processing a workpiece of ferrous alloy. The graph of FIG.2 plots time along the horizontal axis and temperature along thevertical axis. At the beginning of the process, the workpiece is atambient temperature near normal room temperature. In any instance, anambient temperature is a temperature that is sufficiently low so thatsignificant metallurgical transitions will not occur in the workpiece,at least sub austenitic. Typically, ambient temperatures are below 122°F. (about 50° C.).

For illustrative purposes, the ferrous alloy workpiece is heated tofollow a temperature gradient curve, generally indicated by the numeral20. The temperature of the workpiece is rapidly increased on thepositively sloped side 22 of the curve to a temperature of about 723° C.to about 1425° C., and reduced on the negatively sloped side 24 of thecurve back to sub-austenitic, preferably ambient, at a rate of fromabout 315° C./sec to about 6,000° C./sec. For certain aspects of thepresent micro-treating invention, the length of time from ambienttemperature up to the highest temperature and back down to ambienttemperature is from about 0.05 sec. to about 30 sec. One of the usefulaspects of the heating and cooling plateaus would be for them to beidentical and nearly instantaneous, i.e. on the order of fractions of asecond to several seconds, depending on the pull through rate of theworkpiece in relation to the heating/quenching means. The maximum flowrate, and corresponding high strength steel formation rate, willultimately be determined by the ability to fully heat and cool the ironbased alloy with the heating methods provided for the operation. Inother words, if a thick workpiece is being treated, the throughput ratewould logically be slower, as the time it would take to heat theworkpiece to a temperature above the austentizing conversion temperaturewould take longer than a very thin piece.

For example, stamped out car door panels may be heated for less than 3seconds up to a temperature of about 1290° C. and then immediatelyquenched back to ambient temperature within less than 3 seconds, therebyforming high strength areas of Colascite in the portions of the car doorpanel that were desired to be converted by heating and then immediatelycooling only the portions of the panel that are desired to have highstrength. However, these portions may comprise from 1% to 99% of suchcar door panel with respect to its total mass.

Still looking at FIG. 2, curve 22 represents the desired temperaturegradient of the workpiece. In a first portion of a first aspect of theprocess, the workpiece is heated to a temperature at point 26 that isabove the austenizing temperature of the alloy comprising the workpiece.This temperature will vary dependent upon the particular alloy employed;however, one of ordinary skill in the art could readily determine whatthis temperature should be. Some cooling may occur in the time betweenthe maximum desired temperature achieved and the initiation of quenchingdue to atmospheric convection cooling, hence the minor slope in theplateau 26. After being heated, the ferrous alloy is immediatelyquenched according to side 24 of the curve.

In several aspects of the present invention, the step of quickly heatingthe ferrous alloy at least above the austenite conversion temperaturedepends on the microstructure of the material in the startingalloy/article. In traditional plain-carbon steel, austenite exists abovethe critical temperature of about 723° C., while other alloys of steelhave different eutectoid temperatures. The vast majority of ferrousalloys are in the austenitic condition at temperatures in excess ofabout 900° C. In this condition, the temperature in some aspects areabove the austenite conversion temperature may be at least about 985° C.The ferrous alloys may optionally be pre-heated to a temperature belowthe austenitic conversion temperature in the range of about 315° C. to705° C. without making any conversion from the first microstructure to asecond microstructure before being heated above the austenite conversiontemperature. Since the preheating step is below the austenite conversiontemperature, the conversion will not take place until the rapid heatingstep above the austenite conversion temperature.

The step of cooling to the ambient temperature generally happensimmediately after the ferrous alloy reaches the predetermined selectedtemperature that is above the austenite eutectoid temperature. Thecooling rate depends on the moving rate of the ferrous alloys. In oneaspect of the invention involving a fed-through strip of low carbonsteel, the preferred cooling rate was about 315° C./sec to 6,000°C./sec, upon commencement of quenching, when the strip of ferrous alloywas moving at a rate of from about 7.00 IPM (inches per minute) to about20.00 IPM. The heating and cooling of the present invention both happenin a short time, usually within seconds. Consequently, in this example,the heating rate was preferably from about 500° C./sec. to about 1000°C./sec., while the cooling rate was from about 500° C./sec to about5,000° C./sec. A nearly fully Colascitic part results, having around 95%Colascite.

Experimentation has shown that the magnitude of the austenizingtemperature achieved has a direct relation to the prior austenite grainsize in a quenched Colascitic workpiece. Workpieces that have beenrapidly austenized to a maximum of 1000° C. had a prior austenite grainsize of 4 to 6, while those heated to 1320° C. had grain sizes of 1 to3.

With differences in the cooling rate applied to different areas of thisColascitic article, various patterns of microstructure of austenitedaughter phases can also be produced. Although initiation of cooling inmost aspects will occur immediately to form Colascite, full cooling inspecific areas may be allowed to occur more slowly to produce otheraustenitic daughter phases, which then yields a microstructurallypatterned workpiece. For example, hard water quenching to ambientthrough water spray in only certain areas on the surface of the heatedworkpiece can yield Colascite in those areas. Other areas that are aircooled much more gently will return to ferrite. This will produce abainite/ferrite patterned material. Curve 27 shows a rapid heatingprocess 22 followed by a gentle cooling process 28, such as that whichmight be provided by atmospheric convection. Through varied controlledheating and cooling all known austenite daughter phases, includingColascite, can be made in the same steel blank where desired.

In the processing of conventional dual phase materials includingaustenite, traditional metallurgy defines the formation of austenite bythe use of three parameters. First, a lower temperature region A1 wherethe austenite starts to form. Second, a middle temperature range A2where some of the grains are transforming to austenite, and a thirdhigher temperature region A3 with fully transformed austenite. Hence, byheating to various levels of temperature within A2, two phases are made,i.e. some of the grains will still be ferrite, while some will havetransformed into austenite, yielding a dual phase ferrite/austenite mix.As one can imagine, a low A2 temperature would render a mostly ferriticphase, while a high A2 would include mostly austenite.

As dual/multi phase steels are currently made on continuous annealinglines, Colascitic steel sheet and workpieces could be created byreheating in accordance with the third embodiment of the presentinvention. The partially austenized sheet/workpiece could be quenched toyield a combination of highly tempered Colascite and other austenitedaughter phases. If the temperature is rapidly raised to A2 followed bya rapid quench, a dual phase workpiece might be comprised of temperedColascite and untempered Colascite. If the temperature is slowly raisedto A2 and then hard quenched in oil, water, or some other suitablemedium, the dual phase workpiece might be comprised of untemperedmartensite and tempered Colascite. If the temperature is slowly raisedto A2 and then soft quenched or slowly air cooled, the dual phaseworkpiece might be comprised of tempered Colascite and a combination ofpearlite, ferrite, martensite, retained austenite or other austeniticdaughter phases. While the possible options are numerous, the goal ofachieving multiphase steels is to combine the desirable mechanicalproperties of each of the phases present. The best example is asheet/workpiece that forms easily but has elevated strength uponcompletion of forming, taking advantage of the mechanical properties ofColascite.

This distinction of rapid cooling versus gently cooling in at leastportions of the workpiece yields a microstructurally patterned materialthat is very important to automobile makers these days to meet globalwarming and environmental criteria. Dual or multiple phases areachievable by tailor-making the cooling profile to produce differentregions of different materials.

Looking now to FIG. 3, there is shown a workpiece 31 of ferrous alloythat is ready to be transformed to Colascite by one of the methods andapparatus of the present invention. The workpiece 31 is stamped into ashape of a car part, such as a hood. The workpiece is clamped by a pairof ceramic clamps 32 controlled by a computer (not shown). Optionalclamps 34 may also be utilized if required to further stabilize themovement of the workpiece 31. The number of clamps is determined by thereaction of each individual part as it is processed and what is neededto restrain the part properly with respect to the equipment. Acontroller (not shown) may dip or move the workpiece 31 into anapparatus (see FIG. 4), including both a heating and a quenching zone,for transformation. The mode of movement of a workpiece is determined bythe best way to transfer the material. For example, rollers may beemployed for sheet, wire, workpieces, tubes, or rails.

FIG. 4 shows an apparatus, generally denoted by the numeral 40 formaking Colascite in accordance of the present invention. The apparatus40 includes a pair of combined heater and quencher devices 42 as well asa water catch bucket 46. The combined heater and quencher devices 42 maybe controlled by a computer (not shown) to regulate the desirableheating and cooling. Each combined heater and quencher device 42 mayinclude heating blaster nozzles 43, water spray heads 45 and a splashsheet 44 located therebetween. The blaster nozzles 43, which may beheated by propane gas, may be controlled by a volume controller (notshown) in order to raise the temperature of the workpiece from ambienttemperature up to an austenite conversion temperature from about 723° C.to 1,430° C.

For this aspect, the workpiece is heated to about 900° C. to 1,290° C.before being quenched. The water spray heads 45 of the quencher emitcooling medium, preferably water, having a temperature from about 1° C.to 95° C. from a chiller (not shown) to cool the workpiece to ambienttemperature.

In this embodiment, water catch bucket 46 collects and catches coolingwater from the water spray heads 45 for recycling. Splash sheet 44insulates the quenching from the heating, so that the steps of heatingand quenching will not interfere with each other. Although in thisembodiment the heating source is propane and the quenching medium iswater, any suitable heating and quenching means may be used. It shouldbe noted that, based on the particular iron based alloy used, there is acorresponding time between the applied heating and subsequent quench.Therefore, a direct relationship exists between the relative location ofthe heating and quenching means based on a given flow rate to achievethe proper transformation time (i.e. a faster flow rate will result inthe heating and quenching apparatus being further apart).

This heating can be accomplished by any suitable means known in the art.For example, heating may be carried out in a fluidized bed, electricfurnace, plasma furnace, microwave oven, or by an electric resistanceheater, open environment propane forges, gas fired means, solid fuels,and torches. Other heating processes such as inductive heating, flameheating, radiant energy heating and the like may also be employed in thepractice of the present invention. In some instances, it may beadvantageous to measure the temperature of the workpiece during theheating step, and temperature information obtained thereby may beutilized to control the input of heat and/or parameters of the quenchmedium such as temperature, velocity, pressure and the like asappropriate, to allow for accurate temperature control. Such control maybe carried out in a feedback mode or in an indirect mode.

This quench medium may comprise a simple fluid such as water, brinesolutions, other water-based liquid, oil or the like. In some instances,it may be a liquefied or vaporized gas, or solid materials, such aspowder or molten salt. The quench medium may be in the form of a bath inwhich the ferrous alloy article is immersed, or it may include a sprayedvolume of fluid. If the quench medium is a liquefied or vaporized gas,it may comprise a gas including ambient air, an inert gas such asnitrogen, argon or the like, or a reactive gas such as a nitriding orcarburizing gas. In any instance, the quench medium needs to be at avery low temperature compared to the heating temperature. The quenchingmedium is regulated so that the work piece can be cooled down to asub-austenitic, preferably ambient, temperature within seconds.

Various heaters or/and quenchers can be used to heat the ferrous alloys.The heater and quencher may be stationary or movable. An example ofstationary heaters is shown in FIG. 4. The heater including multi-nozzleheating heads, which may be used with a given cross section of ferrousalloys along a path of motion, provides variable heating temperature. Onthe other hand, movable heaters include many variations. Generally,there may be side-to-side movable heaters for contours; up and downmovable heaters for heat variation; combined heater and quencher devicefor moving down to heat and cool, and then move back up for a reheattempering/annealing treatment; hinged movable heaters or anycombinations thereof. The details of the various heaters are disclosedbelow.

Side-To-Side Movable Heater

FIGS. 5A and 5B show a pair of side-to-side movable heaters 52 that maybe used to heat a straight strip of ferrous alloy 51 or it may beconfigured so as to heat an S-shaped strip of ferrous alloy 55. Theside-to-side movable heaters 52 of the present invention may utilize anysuitable heating source. The preferred side-to-side movable heaters 52may be conductive heaters or gas fired heaters. Any suitable device maybe utilized to accomplish the side to side movement of the heater. Forexample, each of the side to side movable heaters 52 may be installed ona rolling bed with bearings that can move the heater in a horizontaldirection shown by an arrow 53. The horizontal movement of the heatersmay control the heating power of the heaters 52. The longer the distancebetween the heater and the ferrous alloy 51 or 55, the weaker theheating power required. For irregular workpieces, side-to-side movableheater 52 may be adjusted according to its contour for a stable heatingprocess. An example is shown in FIG. 5B, where the heater 52 may adjustthe distance between the moving ferrous alloy to maintain the sameheating power.

Up and Down Movable Heater

FIGS. 6A and 6B show a pair of up and down movable heaters 62 that areheating a straight strip of ferrous alloy 61 or an S-shaped strip offerrous alloy 65. The up and down movable heaters 62 of the presentinvention may utilize any suitable heat means. The preferred up and downmovable heaters 62 may be conductive heaters or gas fired heaters. Anyconventional means may be utilized to make the heater movable. Here, asan example, each of the up and down movable heaters 62 is installed on arolling bed with bearings that can move the heater 62 in a verticaldirection as shown by arrow 63, or in an up and down direction as shownby arrow 67. The vertical movement of the heater 67 may control theheating location on the ferrous alloys. For a specific location where itis desired to form Colascite, the up and down heater 62 may concentratethe heating power on the chosen location. When a workpiece isnon-straight, the up and down heater 62, may be adjustable to compensatefor the contour. As shown in FIG. 6B for a non-straight strip of ferrousalloy, the heater 62 may follow the contour of the ferrous alloy tomaintain the same heating effect.

Combined Movable Heater and Quencher

FIG. 7 shows a pair of combined movable heater and quencher devices,generally indicated by the numeral 72. Each of the combined movableheater and quencher devices 72 includes a heater 74 and a quencher 73.As an example, combined movable heater and quencher device 72 isinstalled on a rolling bed 75 with bearings that can move the combinedmovable heater and quencher 72 in a vertical direction as shown byarrows 77. This combined movable heater and quencher device 72 may movedown to heat and quench a strip of ferrous alloy 71 within a close time,and then move back up for reheat if it is desired. The advantage of thecombined heater and quencher may be that the heating and cooling zonesare next to each other, so the heating and cooling happens immediatelyone after the other and Colascite may be transformed within a shortperiod, on the order of seconds. Similarly, the vertical inverse of theaforementioned would also work. This meaning that a quenching meansbelow a heating means with the combination moving upward to makeColascite and then back down for a reheat.

Hinged Movable Heaters and Quenchers

FIG. 8 shows a pair of hinged movable heaters of the present invention,generally indicated by the numeral 80. Each heater includes a heaterplate 81, blaster nozzles 85 and a hinge 83. The hinged movable heatermay be cocked back in a direction shown by an arrow 84, opposite to theheated ferrous alloy 86, to slow down the heating. A hinged quencher isalso contemplated in a similar configuration to the hinged movableheater.

The articles made by the method of the present invention have manyapplications, such as railroad tracks, welded assemblies to be convertedto high strength armor, marine applications, leaf springs, pressureformed stamped pieces for the automotive industry, and 1″ to 84″ wideColascite coils of steel strip. In general, any iron based ferrous alloyarticle that would benefit from by incorporating the mechanicalproperties of a Colascitic microstructure is a candidate to consider.

FIG. 9 shows another embodiment of the present invention and discloses amethod of making controllable high percentage Colascite in ferrous alloynear net shape parts as well as an apparatus for making the same. Asshown in FIG. 9, the process of making Colascite in a ferrous alloyincludes providing a ferrous alloy workpiece 91, heating the workpiece,or portions of, at least above the austenite conversion temperature 92,placing the workpiece of ferrous alloy in the open die 93, closing thedie in the stamping press (not shown) to form a near net shape part fromthe austenized workpiece 94, immediately quenching the workpiece to theambient temperature through convection with the die itself acting as aheat sink, within a very short period 95, and then opening the die andremoving the near net shaped Colascite stamped form 96. The transformedferrous alloy workpiece 96 may have a preferred microstructurecomprising at least about 5% to 100% Colascite. A useful transformedworkpiece would have 50% to 98% Colascite. Various factors, such asstresses, temperature, and the composition of alloys may affect thetransformation to Colascite, and its resulting grain size, and will alsoresult in different concentrations of Colascite. A step of tempering orannealing may be optionally performed later to relieve stresses andprevent cracking of the resulting workpiece.

The process of the present invention may apply to various ferrousalloys. One ferrous alloy may contain carbon in the range of from about0.001 percent carbon by weight (wt %) to about 4 percent carbon byweight (wt %). Another ferrous alloy may contain carbon in the range of0.003 percent carbon by weight (wt %) to 2 percent carbon by weight (wt%), while the carbon content is may also be from about 0.1 wt % to about0.7 wt %.

FIG. 10 is a temperature vs. time diagram illustrating the change oftemperature during the heating and quenching steps for processing aworkpiece of ferrous alloy. The graph of FIG. 10 plots time along thehorizontal axis and temperature along the vertical axis. At thebeginning of the process, the workpiece is at ambient temperature,normal room temperature encountered in the workplace. In any instance,an ambient temperature is a temperature that is sufficiently low so thatsignificant metallurgical transitions will not occur in the workpiece.Typically, ambient temperatures are below about 50° C.

For illustrative purposes, FIG. 10 shows where the ferrous alloyworkpiece is heated to follow a temperature gradient curve, generallyindicated by the numeral 120. The temperature of the workpiece israpidly increased on the positively sloped side 122 of the curve to atemperature of about 723° C. to about 1430° C., and reduced on thenegatively sloped side 124 of the curve back to ambient at a rate offrom about 315° C./sec to about 6,000° C./sec. The length of time fromambient temperature up to the highest temperature and back down toambient temperature is from about 0.05 sec. to about 30 sec. Thepreferred heating and cooling plateaus would identically be nearlyinstantaneous, i.e. on the order of fractions of a second to severalseconds.

For example, sheets of ferrous alloy, or portions of, may be heated forless than 3 seconds to a temperature of about 900° C. to 1290° C., andthen quenched by loading the sheets into a chilled quenching car doorpanel forming die. The die is subsequently closed to form a near netshape car door panel, and then immediately quenched back to ambienttemperature by the cooling process of the chilled die itself within lessthan 3 seconds, thereby forming Colascite in the heated portions of thecar door panel that were desired to be turned into Colascite. Thisprocess can form Colascite in a portion, or the entirety, of the formeddoor panel by heating only the approximate area of the sheet that isdesired to have a Colascite microstructure.

Curve 122 represents the desired temperature gradient of the workpiece.In a first portion of the process, the workpiece is heated to atemperature at point 126 that is above the austenizing temperature ofthe alloy comprising the workpiece. This temperature will vary dependentupon the particular alloy employed; however, one of ordinary skill inthe art could readily determine what this temperature should be. Afterbeing heated, the ferrous alloy is immediately quenched according toside 124 of the curve.

The step of quickly heating the ferrous alloy at least above theaustenite conversion temperature is important. In plain-carbon steel,austenite exists above the critical temperature of about 723° C.; otheralloys of steel have different eutectoid temperatures. The vast majorityof ferrous alloys are in the austenitic condition at temperatures inexcess of about 900° C. The preferred temperature above the austeniteconversion temperature may be about at least about 985° C. The ferrousalloys may optionally be pre-heated to a temperature in the range ofabout 315° C. to 705° C. before being heated above the austeniteconversion temperature.

The step of cooling to the ambient temperature generally happensimmediately after the ferrous alloy reaches the predetermined selectedtemperature that is above the austenite temperature. The heating andcooling of the present invention both happen in a short time, usuallywithin seconds. Consequently, the heating rate is preferably from about300° C./sec. to about 4,000° C./sec., while the cooling rate is fromabout 315° C./sec. to about 5,000° C./sec.

FIG. 11 shows a workpiece 131 of ferrous alloy that is ready to betransformed to Colascite by the method and apparatus of the presentinvention. The workpiece in this example is in sheet form, but couldtake many other forms. Examples of other cross sections are, but notlimited to, I-beams, hollow tubing, C-channel, wire, railroad rails,angle iron, etc. A controller/robotic mechanism (not shown) may move theworkpiece 131 into an apparatus (see FIG. 12), including both a heatingzone and a forming/quenching die, for transformation.

FIG. 12 shows an apparatus, generally denoted by the numeral 140 formaking a Colascite near net shape part in accordance of the presentinvention. The apparatus 140 includes a pair of combined heater devices142 in order to fully austenize the material. The combined upper andlower heater units 142 may be controlled by a computer (not shown) toregulate the desirable heating. Each combined heater device 142 mayinclude heating blaster nozzles 143. The blaster nozzles 143, which maybe heated by propane gas, may be controlled by a volume controller (notshown) in order to raise the temperature of the workpiece from ambienttemperature up to above austenite conversion temperature. In thisaspect, the workpiece is heated to about 900° C. to 1290° C. beforebeing loaded into the die, formed, and then finally quenched. Theforming/quenching die has coolant 144, such as water, flowing throughit. Coolant 144 will have sufficient heat transfer capability to keepthe die cool at a temperature from about about 0° C. to 65° C. from achiller (not shown). Although in this embodiment, the heating source ispropane and the quenching medium is water, any suitable heating andquenching means may be used. It should be noted that, based on theparticular iron based alloy used, there is a corresponding time betweenthe applied heating and subsequent quench.

This die cooling quench medium may comprise a simple fluid such aswater, or more complicated fluids, including brine solutions,pressurized gaseous coolants, other water-based liquid, oil or the like.In any instance, the quench medium needs to be at a lower temperaturecompared to the heating temperature. The quenching medium is regulatedso that the work piece can be cooled down to the sub austenitic,preferably ambient, temperature within seconds.

Various heaters can be used to heat the ferrous alloys. The heater maybe stationary or movable with respect to the stamping die. An example ofstationary heaters is shown in FIG. 12. The heater includingmulti-nozzle heating heads provides variable heating temperatures,possibly different temperatures in different areas of the panel to beformed. The computer control of the heater may control the heatinglocation on the ferrous alloys. For a specific location where it isdesired to form Colascite, the heater may concentrate the heating poweron the chosen location. Areas where Colascite is not desired can beheated to below the temperature required to form Colascite.

The second embodiment of the present invention discloses a pressureforming method of making high percentage Colascite ferrous alloy nearnet shape part and an apparatus for making the same, denoted as “WarmForming”. As shown in FIG. 13, the process of making Colascite ferrousalloy near net shape part includes providing an initially Colasciteferrous alloy workpiece 151, heating the workpiece below the austeniteconversion temperature 152, placing the non-austenized sheet of ferrousalloy in the open forming apparatus 153, operating the apparatus to forma near net shaped part from the non-austenized Colascite sheet 154,optionally quenching the workpiece to the ambient temperature, or someother determined temperature cool enough to prevent distortion of thepart 155, and then opening the pressure forming apparatus and removingthe near net shaped Colascite form 156. A step of tempering 157 may beoptionally later included to relieve stresses and prevent cracking ofthe resulting workpiece. The temperature that the initially Colasciteworkpiece is heated to is that which affords enough ductility toproperly form the part without tearing or otherwise distorting the sheetand damaging the resulting part. This temperature is most often between315° C. and 705° C., but may deviate from this based on the chemicalcomposition of the ferrous alloy being processed. The lower austeniticconversion temperature is to be avoided to prevent any Colascite fromreconstituting back into austenite, which would compromise the finishedpart's integrity.

Experimentation has shown that Colascite has a desirable mechanicalproperty among high strength steel microstructures in that it has theability to retain a significant percentage of its “as quenched” strengthafter multiple thermal cycles to elevated temperatures. For example, anAISI 8620 alloy had an “as quenched” strength of 225 KSI. After multiplethermal cycles to 540° C., the steel retained more than 65% of its “asquenched” strength, still attaining 150 KSI. This is a desirableproperty as many other advanced high strength steels will temper to verylow percentages of their prior strength when heated to this intensitydue to their martensitic microstructure.

As with other aspects of the present invention, various resultingColascite ferrous alloys may contain a Colascite microstructure in therange of from about 1 percent to about 99.999 percent by weight. Otherferrous alloys contain a Colascite microstructure in the range of 30percent to about 97 percent by weight, while the Colascitemicrostructure content most exhibit is from about 50 percent to about 95percent by weight.

FIG. 14 is a temperature vs. time diagram illustrating the change oftemperature during the heating and optional quenching steps forprocessing a workpiece of Colascite ferrous alloy. The graph of FIG. 14plots time along the horizontal axis and temperature along the verticalaxis. At the beginning of the process, the workpiece is at ambienttemperature, such as a normal room temperature encountered in theworkplace. In any instance, an ambient temperature is a temperature thatis sufficiently low so that significant metallurgical transitions willnot occur in the workpiece. Typically, ambient temperatures are belowabout 50° C.

For illustrative purposes, the ferrous alloy workpiece is heated tofollow a temperature gradient curve, generally indicated by the numeral160. The temperature of the workpiece is increased on the positivelysloped side 162 of the curve to a temperature of about 315° C. to about705° C., and reduced on the negatively sloped side 164 of the curve backto ambient at a rate of from about 1° C./sec to about 540° C./sec.

For example, a sheet of Colascite ferrous alloy may be heated for lessthan 3 seconds to a temperature of about 540° C., loaded into the cardoor panel forming die, the die subsequently closed to form a near netshape car door panel, and then optionally quenched back to ambienttemperature by the cooling process of the chilled die itself. Reducingthe temperature to a level at which the steel is less pliable isdesirable to prevent the mechanism that removes the car door panel fromthe die from causing damage to the near net shape panel.

Curve 162 represents the desired temperature gradient of the workpiece.In a first portion of the process, the workpiece is heated to atemperature at point 166 that is below the austenizing temperature ofthe alloy comprising the workpiece. This temperature will vary dependentupon the particular alloy employed; however, one of ordinary skill inthe art could readily determine what this temperature should be. Afterbeing heated, the ferrous alloy is optionally quenched according to side164 of the curve.

FIG. 15 shows yet another aspect where a ferrous alloy workpiece 171 isready to be transformed to a near net shaped part by the method andapparatus of the present invention. The workpiece in this example is insheet form, but could take many other forms. Examples of other crosssections are, but not limited to, I-beams, hollow tubing, C-channel,wire, railroad rails, angle iron, etc. A controller/robotic mechanism(not shown) may move the workpiece 171 into an apparatus (see FIG. 16),including both a heating zone and a forming/quenching die. The mode ofmovement of a workpiece into the die is determined by the best way totransfer the material. Manual labor, mechanized conveyance, and linearmagnetism are just some of the possible ways those skilled in the art ofmaterial handling may choose from to transfer with little detrimentalimpact on the workpiece.

FIG. 16 shows an apparatus known as a stamping die, generally denoted bythe numeral 180 for making a near net shape part in accordance with thisaspect of the present invention. The upper die is denoted as 185. Thelower forming punch can either be one solid block, denoted as 186, or aring/punch combination, denoted as 187 and 188, to use well known“3-piece” forming technology. The apparatus 180 includes a pair ofcombined heater devices 182 in order to heat, while avoiding,austenizing the material. The combined upper and lower heater units 182may be controlled by a computer (not shown) to regulate the desiredheating.

Each combined heater device 182 may include heating blaster nozzles 183.The blaster nozzles 183, which may be heated by propane gas, may becontrolled by a volume controller (not shown) in order to raise thetemperature of the workpiece from ambient temperature up to a levelbelow the austenite conversion temperature. The workpiece is heated toabout 540° C. before being loaded into the die, formed, and thenoptionally later quenched. The forming/quenching die has coolant 184,preferably water, flowing through it. Coolant 184 will have sufficientheat transfer capability to maintain the die having a temperature fromabout 0° C. to about 65° C. from a chiller (not shown) to cool the dieand work piece to ambient temperature.

FIG. 17 shows an apparatus known as a progressive die, generally denotedby the numeral 190 for making a near net shape parts from a steel stripin accordance with yet another aspect of the present invention. Upperhalf 191 of the progressive die complements lower forming half 199.Apparatus 190 includes an induction heating device 192 in which theworkpiece passes through to heat, while avoiding, austenizing thematerial. The heater unit 192 may be controlled by a computer (notshown) to regulate the desirable heating. The workpiece is heated byinduction heater 192 to a temperature which allows ease of metalshearing and forming, preferably about 540° C., before moving totrimming station(s) 194. Strip 198 moves from right to left as thefreshly trimmed strip indexes to the first, of possibly multiple,forming stations 195.

Strip 198 is then indexed through an optional second induction heater193 to maintain the sub-austenitic temperature of the strip. Strip 198is then indexed to a final form station 196 to complete the pressureforming of the part to its final shape. This final form die, or separatecooling station, may be temperature controlled as to quench the part toa temperature at which further shape changing and springback will notoccur. The final form die may accomplish this, either through air blast,water blast, or convection, etc. Cooling means 197 will have the abilityto reduce the temperature of the final formed part to a temperature atwhich its shape will remain stable, usually below 315° C.

Although in this embodiment, the heating source is an induction heaterand the quenching medium is a temperature controlled forming station,any suitable heating and quenching means may be used. This example willbe recognized as a very simplistic example of a progressive die, tothose skilled in the art. Many progressive dies have multiple trimming,forming, piercing, and other differently named stations. This exampleonly illustrates the basics of progressive die forming opportunities andis not intended to limit the number of stations used to achieve a partor to prevent other commonly known processes used in progressive diesfrom being applied to this process.

FIG. 18 shows an apparatus known as a line die, generally denoted by thenumeral 200 for making another near net shape part in accordance of thepresent invention. A line die is simply a sequence of individual diesorganized in a press, or multiple presses, to act as a progressive die,albeit on individual die shoes. Workpiece 208 transfers from station tostation as it may be on a strip, as in a progressive die, or asindividual pieces that are mechanically transferred. Upper half 201 ofthe line die complements lower forming half 209. Apparatus 200 includesan induction heating device 202 in which the workpiece passes through toheat to a temperature below that which will austenize the material.Heater unit 202 may be controlled by a computer (not shown) to regulatethe desirable heating.

Workpiece 208 is shown as a blank or strip, and is heated by aninduction heater 202 to a temperature which allows ease of metalshearing and/or forming, preferably about 1000° F. before the firsttrimming/forming station(s) 204. Blank/strip 208 moves from right toleft and indexes to the next, of possibly multiple, forming/trimmingstations 205. Movement of individual blanks may be accomplished withmechanical assistance, such as that provided by robotics 206. Blank 208may then indexed through an optional second induction heater 203 tomaintain the sub-austenitic temperature of the blank. Blank 208 is thenindexed to a final form station 207 which completes the pressure formingof the part to its final shape.

As in earlier aspects, this final form die, or separate cooling station,may be temperature controlled as to quench the part to a temperature atwhich further shape changing and springback will not occur. The finalform die may accomplish this, either through an air blast, water blast,or convection. The cooling means will have the ability to reduce thetemperature of the final formed part to a temperature at which its shapewill remain stable, usually below 315° C.

Many line dies have multiple trimming, forming, piercing, and otherdifferently named stations and this example only illustrates the basicsof one line die forming unit, and is not intended to limit the number ofstations used to achieve a part or to prevent other commonly knownprocesses used in line dies from being applied to this Colascite formingprocess.

FIG. 19 shows still another die quenching unit as an apparatus known asa roll forming die, generally denoted by the numeral 210. Unlikeprogressive and line dies, in which a stamping press opens and closes toforce the steel to change shape as it is pressurized, a roll forming dieis a single station, or sequence of stations, of multiple formingmembers, usually wheels, which are organized linearly to change theshape of the steel as it is pulled through them. For this example, aflat sheet 211 of Colascite steel will be rolled into a “U” crosssection. The rolling wheels of the forming die 214 restrain the steelfrom multiple directions as shown in the cross section.

Apparatus 210 includes an induction heating device 212 controlled by acomputer (not shown) to regulate the heating to below the austenizingtemperature. The workpiece is heated by the induction heater 212 to atemperature which allows ease of metal shearing and/or forming,preferably about 540° C. before the first rolling station 214. Theworkpiece blank may then be indexed through an optional second inductionheater 215 to maintain the sub-austenitic temperature of the blank, andthen indexed to a final form station 216 which completes the pressureforming of the part to its final shape. This final form die, or separatecooling station, may be temperature controlled as to quench the part toa temperature at which further shape changing and springback will notoccur. The final form die may accomplish this, either through air blast,water blast, or convection.

The cooling means will have the ability to reduce the temperature of thefinal formed part to a temperature at which its shape will remainstable, usually below 315° C. Although in this embodiment, the heatingsource is induction and the quenching medium is a temperature controlledforming station, any suitable heating and quenching means may be used.This example will be recognized as a very simplistic example of a rollforming die, to those skilled in the art. Many roll forming dies havemultiple trimming, forming, piercing, and other differently namedstations. The intention of this example is only to illustrate the basicsof roll forming die forming opportunities and is not intended to limitthe number of stations used to achieve a part or to prevent othercommonly known processes used in roll forming dies from being applied tothis Colascite forming process.

FIG. 20 shows an apparatus known as a fourslide die, generally denotedby the numeral 220 for making a Colascite near net shape part inaccordance of the present invention. A fourslide 221 is just one namegiven to a group of machines that can be set up to act like a multiplehit forming/trimming tool to make intricate small formed parts, capableof high volume production. The apparatus 220 includes an inductionheating device 222 in order to heat but avoid austenizing the Colascitefeed stock 228. The Colascite feed stock 228 may be a wire, strip, orother cross section a four slide will accept. The heater unit 222 may becontrolled by a computer (not shown) to regulate the desirable heating.The workpiece is heated to a temperature which allows ease of metalshearing and/or forming, preferably about 540° C., by the inductionheater 222, before the trimming/forming station(s).

The sub-austenized workpiece 228 feeds into the fourslide as multipleoperations are performed on the workpiece until complete. The final formdie 224, or separate cooling station, may be temperature controlled asto quench the part to a temperature at which further shape changing andspringback will not occur. The final form die may accomplish this,either through air blast, water blast, or convection, etc.

The cooling means will have the ability to reduce the temperature of thefinal formed part to a temperature at which its shape will remainstable, usually below 315° C. The finished workpieces 227 will typicallyfall into a catch basket 225. Although in this embodiment, the heatingsource is induction and the quenching medium is a temperature controlledforming station, any suitable heating and quenching means may be used.This example will be recognized as a very simplistic example of afourslide die, to those skilled in the art. Many “fourslide style” dieshave multiple trimming, forming, piercing, and other differently namedstations. The intention of this example is only to illustrate the basicopportunities of self contained die forming opportunities, a fourslidedie being just one example of the numerous and variedly named machinesthat perform similarly. It is not intended to limit the type of selfcontained forming mechanisms covered by this embodiment or to preventother commonly known processes used in self contained dies from beingapplied to this Colascite forming process.

FIG. 21 shows an apparatus known as expansion hydroforming, generallydenoted by the numeral 230 for making a Colascite near net shape part inaccordance of the present invention. An expansion hydroform die consistsof an upper die half 231 and lower die half 232 that accepts a Colascitesteel tube 234, with openings at both ends of the tube. Hydraulicfittings are clamped to the one half of the die, or the workpieceitself, to cover the two end openings (lower illustrated). When the dieis closed, hydraulic pressure from a hydraulic pump mechanism 233imparted into the inner wall of the tube 234 forces the tube to stretchuntil it contacts the cavity walls of the upper and lower die halves.

The apparatus 230 includes an induction heating device 235 in which thetube passes through to heat but avoid austenizing the material. Theheater unit 235 may be controlled by a computer (not shown) to regulatethe desired heating. In most cases, the workpiece 234 is rough formed toapproximate shape of the die cavities. The workpiece 234 is heated to atemperature which allows ease of metal forming and/or trimming,preferably about 540° C., by the induction heater 235, before the partis placed in the die 232. Alternately the workpiece 234 could be heatedto forming temperature by temperature controlled fluid from thehydraulic pressure unit 233 while it is in the closed die. The die maybe temperature controlled 236 as to convection quench the part to atemperature at which further shape changing and springback will notoccur.

The cooling means 236 will have the ability to reduce the temperature ofthe final formed part 234 to a temperature at which its shape willremain stable, usually below 315° C. Although in this embodiment, theheating source is induction or heated fluid convection, any suitableheating means may be used. This example will be recognized as a verysimplistic example of an expansion hydroform die to those skilled in theart. It should be noted that many expansion hydroform dies can piercethe finished formed part. The intention of this example is only toillustrate the basics of expansion hydroform die forming opportunitiesand is not intended to limit or prevent other commonly known processesused in expansion hydroform dies from being applied to this Colasciteforming process.

FIG. 22 shows an apparatus known as bladder hydroforming, generallydenoted by the numeral 240 for making a Colascite near net shape part inaccordance of the present invention. A bladder hydroform die consists ofan upper die half 241 of the hydraulic bladder and a complementary maleshaped punch/ring lower die half 242 that accepts a Colascite workpiece.Hydraulic fittings 249 are clamped to the upper die half 241. When thedie is closed, hydraulic pressure from a hydraulic pump mechanism 243imparted into the upper half bladder 241 applies force to the workpieceas it is stretched by the lower punch die half 242. The bladder'spurpose is to apply equalized force as the punch stretches the Colascitesteel.

Apparatus 240 includes an induction heating device 245 in which theworkpiece passes through, avoiding austenizing the material. The heaterunit 245 may be controlled by a computer (not shown) to regulate thedesirable heating. The workpiece 244 is heated by the induction heater245 to a temperature which allows ease of metal forming and/or trimming,preferably about 540° C., before the part is placed on the die 242. Thedie may be temperature controlled 246 as to convection quench the partto a temperature at which further shape changing and springback will notoccur.

Cooling means 246 will have the ability to reduce the temperature of thefinal formed part 244 to a temperature at which its shape will remainstable, usually below 315° C. Although in this embodiment, the heatingsource is induction, any suitable heating means may be used. Thisexample will be recognized as a very simplistic example of a bladderhydroform die to those skilled in the art. The intention of this exampleis only to illustrate the basics of bladder hydroform die formingopportunities and is not intended to limit or prevent other commonlyknown processes used in bladder hydroform dies from being applied tothis Colascite forming process.

FIG. 23 shows an apparatus for liquid punch hydroforming, generallydenoted by the numeral 250 for making a Colascite near net shape part inaccordance of the present invention. A liquid punch hydroform dieconsists of an upper die half 251 and a complementary lower die half 252that accepts a Colascite sheet 254. Lower die half 252 shows only arepresentation of the finished part's outer edge 258. Within this edgearea is a hydraulic fluid flow cavity 257. Lower die half 252 has ahydraulic fluid pressure fitting through which fluid will flow. When thedie is closed, upper die half 251 seals against the finished edgerepresentation on the lower die half 252. Hydraulic pressure from ahydraulic pump mechanism 253 imparted into the fluid flow cavity forcesthe sheet to stretch until it contacts the cavity walls of upper diehalf 251.

Apparatus 250 includes an induction heating device 255 in which thesheet passes through to heat, while not yet austenizing the material.Heater unit 255 may be controlled by a computer (not shown) to regulatethe desirable heating. In the spirit of the second embodiment, theColascite workpiece 254 is heated to a temperature which allows ease ofmetal forming and/or trimming, preferably about 540° C., by theinduction heater 255, before the part is placed on lower die 252.Alternately the workpiece 254 could be heated to about 540° C. bytemperature controlled fluid from the hydraulic pressure unit 253 whileit is in the closed die. Upper die half 251 may be temperaturecontrolled as to convection quench the part to a temperature at whichfurther shape changing and springback will not occur, usually below 315°C.

In the spirit of the first embodiment, the non-Colascite workpiece iseither heated by induction to about 900° C. to 1290° C. and placed onthe lower die 252 or the temperature controlled fluid from the hydraulicpressure unit 253 rapidly heats the workpiece to about 900° C. to 1290°C. when the workpiece is placed in the closing die. The heatednon-Colascite material is stretched by the heated hydraulic fluid untilit contacts the temperature controlled upper die. The upper die quenchesthe non-Colascite steel to form the Colascite microstructure. Coolingmeans 256 reduces the temperature of the final formed part 254 to atemperature at which its shape will remain stable, usually below 315° C.Again, although in this embodiment, the heating source is induction orheated fluid convection, any suitable heating means may be used. Thisexample will be recognized as a very simplistic example of a liquidpunch hydroform die to those skilled in the art.

FIG. 24 shows a third embodiment with all aspects of the secondembodiment (see FIG. 16 through FIG. 23) but one. In some instances, anexception to sub-austenitic processing may exist. It may be desirable tosurpass the lower austenitic conversion temperature for a predeterminedtime frame, to a predetermined temperature, in order to allow a specificpercentage of daughter phase microstructure to re-convert to parentaustenite. This parent austenite may then be processed into differentdaughter microstructures that would yield properties dissimilar to theprior daughter phases still present in the sheet. To not be repetitive,a restatement will not be made of all of the statements and techniquesof pressure metal forming described for the second embodiment (see FIG.16 through FIG. 23), but will say that the resulting microstructuresfrom the second embodiment described will work for the third embodimentwith a modification to A2 austenitic temperature range processing, whichis commonly between 723° C. and 900° C. for many steel alloys.

The third embodiment of the present invention discloses a method ofmaking high percentage Colascite multiphase ferrous alloy near net shapeparts and an apparatus of making the same. As shown in FIG. 24, theprocess of making Colascite multiphase ferrous alloy near net shape partincludes providing an initially Colascite ferrous alloy workpiece 261,heating the workpiece to surpass the lower austenitic conversiontemperature to a predetermined temperature 262, placing the partiallyaustenized workpiece of ferrous alloy in the pressure forming apparatus263, and applying forming pressure to form a near net shaped part fromthe partially austenized Colascite sheet 264. The next step offers amultitude of options to create different daughter microstructures fromthe austenized portion of the workpiece. Cooling from austenite throughhard quenching, quenching and tempering, quenching and partitioning, airknife cooling, slow cooling, etc and many other methods known to thoseskilled in the art will yield a tempered Colascite multiphase material.

Upon the workpiece reaching ambient temperature, or some otherdetermined temperature cool enough to complete microstructuraltransformation and to prevent distortion of the part 265, the die isopened and the near net shaped Colascite multiphase pressure formedworkpiece 266 is removed. A step of tempering 267 may be optionallylater included to relieve stresses and prevent cracking of the resultingworkpiece. The temperature that the initially Colascitic sheet is heatedto is that which affords enough ductility to properly form the partwithout tearing or otherwise distorting the sheet and damaging theresulting part. This temperature is most often between 723° C. and 850°C., but may deviate from this based on the chemical composition of theferrous alloy being processed.

FIG. 25 is a temperature vs. time diagram illustrating the change oftemperature during the heating and optional quenching steps forprocessing a workpiece of Colascite ferrous alloy. The graph of FIG. 25plots time along the horizontal axis and temperature along the verticalaxis. At the beginning of the process, the workpiece is at ambienttemperature, normal room temperature encountered in the workplace. Inany instance, an ambient temperature is a temperature that issufficiently low so that significant metallurgical transitions will notoccur in the workpiece. Typically, ambient temperatures are below about50° C.

For illustrative purposes, the ferrous alloy workpiece is heated tofollow a temperature gradient curve, generally indicated by the numeral270. The temperature of the workpiece is increased on the positivelysloped side 272 of the curve to a temperature of from about 315° C. toabout 850° C., held above the lower austenitic conversion temperaturefor a predetermined timeframe 276, and then reducing its temperature onthe negatively sloped side 274 of the curve back to ambient at a rate offrom about 1° C./sec to about 5,000° F./sec. The preferred heating andcooling plateaus are ferrous alloy specific. The most importantcharacteristic of the curve is to decompose the designed amount ofdaughter microstructure back into parent austenite before creating newdaughter microstructures to yield a new Colascite multiphase workpiece.

For example, a sheet of Colascite ferrous alloy may be heated to atemperature of about 760° C., held at 760° C. for enough time to return20% of the microstructure to austenite, loaded into the car door panelforming die, the die subsequently closed to form a near net shape cardoor panel, and then optionally quenched back to ambient temperature bythe cooling process of the chilled die itself. Reducing the temperatureto a level at which the steel is less pliable is desirable to preventthe mechanism that removes the car door panel from the die from causingdamage to the near net shape panel of 20% martensite in an 80% Colascitematrix.

FIG. 26 represents a fourth embodiment of the present invention and isan expansion of the second and third embodiments. Although most of theprevious embodiments discuss heating the workpiece in the vicinity of,but outside of, the exact pressure forming area through induction orheating heads, the unformed Colascite workpiece could also be heated inan environmentally controlled pressure forming general area. Withoutrestating each embodiment mentioned above, each embodiment could beconstructed in an elevated temperature, atmospherically controlled workenvelope. Pressure forming apparatus would be constructed of materialssuited to operating in an elevated temperature environment. Through thisembodiment, workpiece cooling, to the open environment, would not bedetrimental to the process and proper forming temperatures would bemaintained at all times.

For example, the second embodiment of a progressive stamping dieapparatus 280 could be designed with an insulated containment 282 on itsfour vertical sides. The part could be heated by the initial inductionheater, passed through and processed in an environmentally controlledelevated temperature die, and then cooled upon exiting the finish partside of the tool. The insulated containment panels could be affixed tothe lower half of the progressive die 284. The upper half 286 of theprogressive die would traverse up and down maintaining a thermal barrierwith the insulation that is affixed to the lower die half 284. Theworkpiece 283 entering the insulation enclosure would have a slot 288 toreceive the incoming Colascite workpiece. The insulation, throughflexible contact, would be arranged as to prevent as much heat transferout of the insulated environment as possible. The finished part 289would exit the progressive die through a “trap door style” slot 287 thatwould open as the workpiece indexes. Heating of the insulatedenvironment could be done in a variety of methods, all aforementioned inprior embodiments of this application.

Although in these embodiments, the heating source is either propane orinduction and the quenching medium is a temperature controlled formingstation, air knives, water, etc, any suitable heating and quenchingmeans may be used. It should be noted that, based on the particular ironbased alloy used, there is a corresponding time between the appliedheating and subsequent quench to prevent part distortion. It should alsobe noted that particular Colascite alloys may be better served by beinginitially quenched to higher temperature than a water mechanism willallow and then allowed to cool to room temperature by other means. Thewater cooling of the dies may also be substituted by heating oils inorder to maintain the dies at a certain temperature and the part noteven cooled until after it exits the die.

This heating for any of the above embodiments can be accomplished by anysuitable means known in the art. For example, heating may be carried outin a fluidized bed, electric furnace, plasma furnace, microwave oven, orby an electric resistance heater, open environment propane forges, gasfired means, solid fuels, and torches. Other heating processes such asinductive heating, flame heating, radiant energy heating and the likemay also be employed in the practice of the present invention. In someinstances, it may be advantageous to measure the temperature of theworkpiece during the heating step, and temperature information obtainedthereby may be utilized to control the input of heat and/or parametersof the quench medium such as temperature, velocity, pressure and thelike as appropriate, to allow for accurate temperature control. Suchcontrol may be carried out in a feedback mode or in an indirect mode.

This die cooling quench medium may comprise a simple fluid such aswater, brine solutions, or other water-based liquids, oil or the like.In any instance, the quench medium needs to be at a lower temperaturethan the heating temperature. The quenching medium is regulated so thatthe work piece can be cooled down to the ambient temperature withinseconds or longer as desired, based on the required characteristics ofthe given Colascite iron based alloy.

Various heaters can be used to heat the Colascite ferrous alloys. Theheater may be stationary or movable with respect to the stamping die. Anexample of stationary heaters is shown in FIG. 16. The heater includingmulti-nozzle heating heads provides variable heating temperature,possibly to different temperatures in different areas of the panel to beformed. The computer control of the heater may control the heatinglocation on the ferrous alloys. For a specific location where it isdesired to form more easily in the die, the heater may concentrate theheating power on the chosen location.

The articles made by the method of the present invention have manyapplications. In general, any pressure formed iron based article thatwould benefit from a Colascitic microstructure is a candidate toconsider. It should be noted that some iron based alloy high strengthnear net shaped parts may require multiple operations to achieve finalform.

A least one first hot forming process in accordance with the presentinvention almost instantaneously creates a Colascite microstructure uponquenching. The second set of pressure forming embodiments of thisprocess is dissimilar to prior hot forming processes because it is theonly hot forming process that is specifically designed to work with apre-existing Colascite microstructure steel. Furthermore, it is thefirst hot forming process in which the ultra high strength of the steelmicrostructure maintains approximately 65% of its as quenched strengthafter multiple thermal cycles to 540° C. which makes the steel moreductile and easier to form.

Moreover, it is thought that this is the first hot forming process inwhich the steel can be continually reheated to form again and again,without significantly degrading strength. Reheating may be necessary forforming processes in progressive dies, line dies, flanging dies, smallpart making fourslide dies, etc. The second embodiment is a unique hotforming process in which the formation of austenite is specificallyavoided, not intentionally passed to make another daughtermicrostructure upon quenching, such as in die quenching technology whichmakes an untempered martensitic structure. The third embodiment is aprocess in which high strength Colascite may be slightly degraded byintentionally passing the lower austenitic conversion temperature togain a specific percentage of non-Colascite microstructure therebyforming a dual or tri phase Colascite material with subsequent coolingand/or quenching.

Another interesting aspect of this invention's embodiments is that aninstant heat tempering process, of approximately 315° C. toapproximately 720° C., that is subsequently water quenched, causes moreColascite to nucleate in the iron based alloy workpiece. Heating may bedone by propane/oxygen flames, induction, microwave, or any otherpreviously mentioned heating methods known to those skilled in the art.Quenching may be done by water, oil, aqueous solutions or any othermethods that produce the required temperature drop in the Colasciteworkpiece.

Partial and Full Colascite Transformation

In the course of studying the photomicrographs taken of the materialwhich has been produced by the previously described microtreatmentprocess of the present invention, it has been noted that the iron-basedalloy has various sections, grain boundaries and microstructures whichindicate formation of various materials made by this new process. Thematerials included in the photos show Colascite, bainite-like,martensite-like, acicular ferrite-like, austenite-like, and otherunknown materials, along with combinations of the above.

These partially and fully transformed Colascitic portions may includeconversion of between 1 and 99 percent by volume of the material intoColascite, while the remaining material may be a combination of othermaterials including martensite, austenite and combinations of thosematerials all together. Such materials generally tend to have more thanhalf Colascite after following the process, but sometimes it is over 90%and sometimes it is less then 10%, depending on how much of the area wastreated.

A stamped out car door panel in which the areas around the A and Bpillars and the exterior edges are desired to be transformed intoColascite, while leaving the steel door in its original form ofuntreated stamped coiled steel for other desirable properties, ispossible with the present invention. Therefore, the portions of the doorpanel that would be treated, to yield a piece that had maybe as much as5% of the area transformed into Colascite. On a more microscopic level,the edge that was treated would be nearly all Colascite, depending onhow diligent the processor was in heating and quenching immediately.

It must also be understood by other material scientists that when it isstated that “partially and/or fully transformed to Colascite” it ismeant that at least portions of the article being treated convert or aretransformed to Colascite, which leaves untreated materials in theiruntreated state, and also means that incomplete treatments createdifferent microstructures and materials, while sometimes it is desirableto have only partially transformed Colascite, such as with the case ofthe car door panel described hereinabove.

Temperature Control

In accordance with the above, the present invention has been practicedwith many variations, especially those in the areas of temperaturecontrol and various transformations have occurred, when following theprocess of the present invention. Temperature control is an importantaspect of this invention and such control is important to the formationof various partially and fully transformed Colascitic portions ofiron-based alloys. For example, many samples of steel that have beenraised to 1050° C. to 1320° C. generally have been yielding 90%Colascite, while raising the temperature to 980° C. is yielding about75% Colascite. This invention may still be practiced over 1370° C. tojust below the melting point of the steel being utilized. Of course,different steel alloys require slight experimentation in order toachieve the desired amount of Colascite. Of course, because every singlepossible steel cannot be listed that is available to mankind,description is needed of the temperature control situation for each ofthose examples.

The temperature of the subject alloy is rapidly raised to a temperatureabove the austenitic temperature of the material, and then immediatelyquenched in order to achieve Colascite, coalesced bainite, bainite, orvarious versions of martensite. Various professors and metallurgistsdiffer on their impressions as to the microstructure achieved by thepresent process, and it is reluctantly stated that it is always bainiteor martensite that is being formed, hence Colascite is the name givenuntil the experts determine exactly what to call it.

Looking now to FIG. 27, it can be seen that a sample of AISI 8620 steelwas converted to what appears to be Colascite by this processing ofrapidly heating to a temperature above the austenizing temperature, i.e.1290° C., and immediately quenching within fractions of a second to forma predominantly bainite structure. FIG. 27 shows the predominantlyColascitic structure. FIG. 28 shows the identical steel, AISI 8620,austempered in molten salt for 15 minutes. Clearly, the microstructureformed by that traditional process does not bear any resemblance to theColascite of FIG. 27.

Yet, when viewing FIG. 29, an AISI 8620 material having cobalt andaluminum alloyed therein to increase bainitic transformation wasprovided as the starting material, molten salt was used to quench theaustempered portion, yielding a resulting microstructure which revealswhite areas which appear to be retained austenite and “classicalbainite”.

The starting material, may be of any cross section, including wire,rolled coiled steel, stamped pieces, of any thickness that can be heatedand quenched in a relatively short period of time. The present processworks to form new microstructures. The process works especially wellwith materials that are from about 0.001″ to 0.5″ cross sections,including wires, strip steel, and the like, as they are easy to heat andquench. With appropriate rapid heating means, thick sections in excessof 1″ to 2″ can be obtained.

The temperature may be raised on the material to a temperature above theaustenitic conversion temperature, but especially between 900° C. and1370° C. in any manner which allows the steel to be handleable, i.e. sothat it is not melting and can still be handled. However, the quenchrate must be between 500° C. per second to about 6,000° C. per second,i.e. the temperature of the steel is generally in the neighborhood of900° C. to 1370° C. and must be quenched immediately to sub-austenitic,preferably room, temperature. Studies done with boiling water as aquenchant have shown Colascite to be formed in the resulting steelleading to the belief that slack quenching may not be detrimental toColascite formation. Whereas many other material properties suffer froma slack quench of hot water, Colascite forms regardless.

The rate of heating may be at any rate, such that the steel may bepreheated in a large oven in a coil an then boost heated at the very endat a rate of 500° C. per second as it passes between the heater units,only to be quenched immediately thereafter within three seconds to roomtemperature.

The method of heating and quenching is optimally suited to everypractice of the invention, such that the heating may be effected by gastorches, infrared, conduction, or any of the methods described in theabove mentioned provisional patent applications, but may also includeheating with high temperature rollers, as well as quenching with verylow temperature rollers made of alloys that can resist such temperaturesand also that can impart thermal transport at a very quick rate. Heatdissipation materials may be used for the quenching rollers, and suchrollers may include materials such as various heat dissipative ceramics,i.e. silicon nitride, and/or any other heat transfer material that willimmediately remove heat from the steel. While the quenching rate isdramatic, materials suitable for chilling with the rollers may mean thatthe exterior body of a particular roller that comes in contact with theheated steel or other heated iron-based alloy being microtreated, mustbe able to remove heat at the rates described above.

Furthermore, preheating under the austenitic temperature may beadvantageous to get the materials into a high temperature state, whereelemental migration can begin, but at a sufficiently low temperaturei.e. between 200° C. and 650° C., as the material should not austenitizeprematurely. In addition, in order to avoid de-carburizing under 1200°C., it is best for an operator to select relatively quick heating andquenching times because the treatment is not occurring for long enoughat a particular temperature point to allow the carbon to escape.

The optional preheating step may be used to bring the material up to200° C. to 650° C., and then given a “boost heat” immediately prior toquenching. The method of adding the additional “boost heat” may be thesame preferred gas or propane torches described in the various otherprovisional patent applications. Such torches may be constructed withtorch orifices or blowtorch heads, directed toward the steel to bemicrotreated. By staggering the blowtorch heads, for example, in thecase of rolling strip steel, one side of the opposing panels ofblowtorch heads could have an odd number of heating points, while theopposite side would have an even number such that they are staggered inbetween each other, so that, in the instance where one of the torchheads became clogged or was otherwise non-ignited, the remaining headswould sufficiently carry the day in order to achieve the goal ofmicrotreatment.

Feed Rate

In accordance with yet another one of the embodiments of the presentinvention, where tensioning rollers may be utilized along with acontinuous roll of wire or strip steel, the feed rate of the continuousmaterial is a factor in the heating and quenching rate that is usablefor the invention. For example, a 75 mm wide strip steel is generallyheated by a bank of a multiplicity of torch heads and immediatelythereafter, i.e. within several inches of the heating bank, the stripsteel comes into contact with a cooled water chill quench bucketconfiguration that has a slit in the bottom of the bucket surrounded byrubber seals in order to minimize loss of the cool water that is usedfor quenching. The feed rate may be from about 25 mm per hour to abouttwo kilometers per minute, depending on how fast the heaters are able toheat the steel and how quickly the water quench bucket can be used tocool the heated steel immediately after the heating has taken place. Thestrip steel mentioned above may be rapidly moved through the tensioningrollers either horizontally, vertically or at any angle that may bepreferential. The feed rate is easily calculated by the ability of theheaters to heat whatever subject iron-based alloy is being microtreated.

Feed rates will differ for microtreating continuous materials other thansteel, as this invention may be utilized for any metallic alloy in orderto perform a phase transformation, from untreated to treated. Thepresent inventors envision that any material capable of withstanding aheat treatment followed by an immediate quenching is a candidate forphase transformation by the method of the present invention.

For instance, a 75 mm wide strip steel can be fed through the blowtorchheater bank and water quenched at a rate from about 25 mm per hour toabout 2 meters per second. The heating block which is used in this“flash processing” procedure is preferably located approximately 10 to250 mm above or beside the water quench station so that immediatequenching may be effected. As feed rate increases, so too may thepreferred distance between rapid heating and subsequent quenching. Somematerials may need an alloy dependent prescribed amount of time at anelevated temperature to “prepare” for transformation to the desiredmicrostructure.

It is anticipated that ultimately the present invention may be practicedat a feed rate of up to one mile per minute in order to treat steel asit passes therethrough. If the subject steel is thicker, the heatingstep will take longer, and the feed rate will be consequently lengthier.

Alloying Components

Alloying of the stock feed material, i.e. the iron-based alloy, cancreate different effects after quenching. Certain components may beadded for thermal transport such as cobalt, aluminum, helium, nitrogen,hydrogen, and other known thermal transport components, which will allowa thicker material to be microtreated because the heating rate will beincreased, and the quenching rate will be increased. For the cobaltcomponent, it is preferable to have less than or equal to 1.5% byweight, aluminum preferably less than or equal to 1.0% by weight, andthe hydrogen, helium and nitrogen components may be incorporated asmetal hydrides by infiltrating the metallic microstructure matrix withhydrogen gas, helium gas and/or nitrogen gas. Any combination of thesethermal transport components is also envisioned by the present inventionand may act to provide microstructure transport mechanism through grainboundaries and through the bulk of the material.

The materials that are formed by the present invention appear to becombinations of Colascite possibly comprised of upper bainite, lowerbainite, coalesced bainite, martensite and combinations of the above.Upper and lower bainite is commonly and conventionally formed byaustempering to lower and higher temperatures, respectively, on theorder of from about 220° C. to 360° C. for lower bainite and 360° C. to550° C. for upper bainite, each steel alloy having its own determinedtemperature ranges. Coalesced bainite is formed when the platelets ofbainite that are created simultaneously in parallel orientation, mergetogether to form coalesced materials that are larger pieces of bainite.

In order to control and reduce the coalesced bainite concentration, itanother aspect of the invention incorporates alloying with new materialsto control the amount of the different types of possible bainitecomponent. The present invention has been shown, on numerous occasionsusing the examples shown hereinbelow, to provide a much higherconcentration of particularly desired bainite-like material. Alloying,such as keeping the carbon concentration at a lower weight percentagevalue, has been found to reduce or prevent coalescing, which may alsoact to process out the coalesced bainite. In order to further decreaseor prevent coalescing, the present invention envisions adjustments ofthe heating and quenching temperatures, and adjusting the feed rate anddraw rate of the coiled or strip steel or steel wire as it is receivedthrough the heating element and the quenching station. In addition, inthe embodiment utilizing the tensioning situation with the feed rate anddraw rate at variable rates, it has been found that the more onestretches the sample, the more aligned the platelets become, giving morechance for coalescing to occur. Initial experiments indicate thatgreater stretching of the steel between the tensioning rollers tends toproduce more coalescing, which is less desirable.

Rapidly heating to a high temperature then immediately quenching backdown to room temperature within milliseconds, revealed that it is alsopossible to put a surface effect onto a bulk material, whereby aColascitic skin could be put on the outside of a steel core piece. Forexample, a 6.5 mm plate of AISI8620 steel could be briefly heated andimmediately quenched in a manner such that only an outer skin or layerof the Colascite, or whatever material it is that the present inventionis providing, is formed. Furthermore, spots or regions of this new highstrength material could be formed across the surface of core piece ofsteel, such that a pattern of Colascite could be formed as a surfaceeffect of a relatively thick piece of steel. The heating of the surfacecould be performed by the propane or gas torch as previously describedin reference to the provisional patent applications already on file,such that a desired pattern could be treated onto the surface of a largepiece of untreated steel.

For instance, a 6.5 mm thick piece of steel which is 1.3 meters wide and2.5 meters tall could be used for architectural components and buildingsupplies, wherein it might be desired to have an extremely strongportion for mounting to the sides of a skyscraper. In that regard, the1.3×2.5 meters sheet of metal could be run through a microtreatmentprocess whereby only the edges and the center of the 6.5 mm steel platewould be heated and followed by an immediate quench in order to formColascite, or some other very strong material only in the places that itwas heated. Therefore, the steel plate would remain untreated in theportion that was not heated and not quenched. This may be necessary formounting, or to provide resistance to bending in certain parts of abuilding where a steels flexural modulus was needed to keep the buildingstanding in the event of an earthquake.

The layers of Colascite, or other formed hard materials of the presentinvention, can be calculated to a particular depth by determining howlong it would take to heat to a particular layered depth that wasdesired, and thereafter immediately quenching with water in order toprovide a toughened steel. Furthermore, it may be discovered that alayer across the entire surface of an architectural steel component maybe desired in order to resist earthquake and/or tornado, etc.individually described by category.

FIG. 30 illustrates an embodiment of the present invention as it relatesto the processing of hollow tubes, like those used for flagpoles andpipe. Only one side of the material of the iron base article can receiveintense heat applied to it and quenching means contacting it. In theinstance of a lengthy hollow pipe 292 shown in FIG. 30, it is easy toenvision that only the outside of the pipe can have an oxy/propane torchhead 290, or other heating means, apply direct heat by flame points 290a to it. Tube 292 may travel downwardly through a hole in water bucket291 containing water 291 a. Around the hole it is possible to use asealing means (not shown) to keep in most of the water that would leakout. The leaking water can be recirculated into the chiller unit, ifused, and fed back up into the water bucket 291. It is inconvenient toapply heat to the inside of sections of very long continuous, closedcross section piping. The heat that reaches the inside surface of thepipe does so through conduction in the metal itself. As well, the act ofquenching is accomplished as a cooling “shockwave” that proceeds fromthe outside pipe wall to the inside surface through a mode similar tocooling convection. Flat steel sheet need only be heated and quenchedfrom one side to attain Colascitic, bainitic and/or martensitic, etcmicrostructures.

FIG. 31 illustrates another aspect in which a microstructuraltransformation occurs on a previously stamped iron based article, suchas an automotive hood 293, that has not yet been converted to Colascite,bainite and/or martensite, or any of the other high strength materials.In particular, an automotive panel such as a outer stamped hood panel293 could be heat treated by flame heating 294 a , using movable heatingheads 294. In this aspect, quenching by quench unit 295 with quenchant295 a may be performed on both sides of the hood, while austenizing heatneed only be applied to one side of the article. Additionally, theconverse is also found to be effective. As in hollow piping, heat willconduct through the cross section of the article to fully austenize thematerial. For example, application of heat to only one side of a stampedarticle, whose outside surface of material (OSM) will be painted, leavesthe OSM more uniform and ready to accept such painting treatment withoutthe need to remove scale or other heat treating marks.

The resultant Colascitic grain size is controllable due to the magnitudeof the austenization temperature. It has long been known that the sizeof the grain, and similarly modifiable bainitic platelet size, has astrong correlation to the mechanical properties of the steel. Smallercolascite/bainite platelets will typically yield higher strength andmore elongation. More extreme temperatures in the vicinity of 1320° C.tend to yield larger grain size and larger colascitic/bainitic plates.Lesser temperatures around 980° C. to 1040° C. have a tendency toproduce smaller grain and plate sizes. Therefore, it is desirable toaustenize at lower temperatures before the higher temperature treatmentof the present invention as to achieve a smaller grain size, with itsresulting higher strength.

FIG. 32 shows a roll hemming aspect of the present invention. Rollhemming as shown in FIG. 32 is a process may be used to attach a layeredpanel of steel with another. An example of this occurs in the productionof traditional automotive hood assemblies. The outer hood panel 296 isstamped with its outermost flanges at 90 degrees open to accept an innerhood panel 296 a. Once inner door panel 296 a has been placed insideouter hood panel 296, pressure applying rollers 298 are used to foldover, or hem, the outer hood panel's flanges 297 to lock the inner hoodpanel in place. As hood outer panels could be made from predominantlyColascitic steel, heat would be applied to the flange area to enablepressurized rolling to occur more easily. The heat could be appliedthrough numerous means, including but not limited to, an oxy/propanetorch 299 which applies heat immediately before the pressure applyingrollers 298 hem the flange.

FIG. 33 illustrate a variation of the movable head concept that mayapply to all methods of heating an iron based article as well as thequenching mechanisms. In this aspect, a locked together successivecombination of heating and quenching units can be rolled up the lengthof a workpiece in the direction of arrow 318 to successively heat andquench the workpiece. The successive combination of heating andquenching units, such as heating 311, quenching 312, heating 313,quenching 314, heating 315, and quenching 316 of an iron based articlecan be developed with repeating or many varied microstructures andstrength levels. It is possible that the entire article, or any portionthereof, may be thermally cycled to change the microstructure.

Still looking at FIG. 33, a first heating mechanism 311 will inducerapid austenization of the iron based article. The first quenchingmechanism 312 will complete the immediate transformation to Colascite.The next heating mechanism 313 in the thermal cycling of the iron basedarticle reheats portions of up to and including the entirety of theColascite microstructure of the article. Tempering to a temperaturebelow A1 where austenite starts to form, or intercritical annealing to atemperature between A1 and A3, i.e. A2, can be induced by this secondheater 313 and it will occur in a relatively short time after theinitial Colascite forming heat/quench. This tempering or annealing canbe varied at levels of thermal intensity to affect different locationsof the iron based article to yield various strength levels. The secondquench may be applied by the quenching mechanism 314.

Third heater 315 is next to a third quencher 316. Although tempering isthe more common thought, intercritical annealing may also be performed.The third temperature modification in the thermal cycling of theColascite article may include an optional quench. Depending on theheating intensity applied to the Colascite article, this optional quenchmay or may not change the microstructure. In cases of low leveltempering intensity, quenching may do little beyond reducing the waitingtime before which the Colascite article can be easily locationallymanipulated by mechanical conveyance. In cases of higher level temperingintensity, such as those involving intercritical annealing, this quenchcan induce the creation of multiphase microstructures by creating newaustenite daughter phases in accordance with the third embodiment. Incontinued cycling, additional heating and quenching cycles may proveuseful to further refine the Colascitic microstructure.

FIG. 33 shows an apparatus capable of this multiplicity of thermalcycling, which can be described as follows. To perform heating andquenching to nucleate Colascite, intercritical annealing portions ofColascite, and then tempering portions of Colascite, three heating headswould have three quenching heads interspersed in the pattern 311, 312,313, 314, 315, and 316 as shown in FIG. 33. The first heating head 311would follow the contour of the iron based article 319 as to rapidlyaustenize it to the desired temperature. The contour following path ofhead motion is denoted as 318. The first quenching head 312 would followthe article contour and immediately quench the article to formColascite. The second contour following heating head 313 would raise thetemperature of the article to appropriately induce intercriticalannealing. The second quenching mechanism 314 could lower the articlestemperature to modify Colascite to the desired microstructure. The thirdcontour following heating method 315 would once again raise thetemperature to the desired thermal level to induce tempering. The third,and optional, quenching means 316 would finally lower the temperature ofthe article to be locationally manipulated.

FIG. 34 shows another configuration that would accomplish the sameresults by incorporating multiple passes of a lesser number ofheating/quenching mechanisms. For example, in the first path of motion328, the contour following heating means 321 could rapidly austenize theiron based article 329. The first pass of the contour followingquenching means 322 would form the Colascite microstructure. The heatingmeans could then initiate an intercritical annealing step by followingthe same path of motion 328 it had followed during completeaustenization, just at lower intensity to the appropriate temperature.The quenching means would similarly follow the same motion as before toappropriately change the microstructure. As a final step, the heatingand quenching means would follow the path of motion 328 for a third timeto temper and optionally quench the iron based article.

Any multiplicity of the above embodiments could occur for a specificapplication. It is possible that the aforementioned H, Q, H, Q, H, Qthermal application head could actually be Q, H, Q for different inversepaths of motion or any other combination that will suit this applicationfor a specific iron based article.

In reference to all the above heating operations, many methods ofimparting heat to the iron based article will work in both reactive andnon-reactive atmospheres. The atmospheric pressure is equally modifiableto desired levels of pressure for various purposes. Electric resistance,magnetic, laser, x-ray, induction, gaseous fuel, and many other methodsknown to those skilled in the art will suffice to develop rapidaustenization of the iron based article.

Regarding quenching operations, both reactive and non-reactive gaseous,liquids, and solids may suffice to adequately quench the iron basedarticle. Liquids may be organic or inorganic. Appropriately temperaturedwater, salts, zinc, aliphatic and non-aliphatic oils, and the like mayconstitute the quenching bath. In the case of solid and semi-solidquenchants, metallic salts, powders, and particulates with their meshsize ranging from talc to that of pea gravel will suffice.

While this potential multiplicity of thermal cycling is occurring,coatings with desired properties may be applied by creating conditionsconducive to such activity. Applying coatings such as silaceous carbide,zinc for galvanizing, and titanium nitride may all benefit the ironbased article's properties if applied at the appropriate temperaturesrequired. Other coatings exist, as the above three mentioned being onlyexamples in a list of options too numerous to mention.

In accordance with the above, the present invention has been practicedwith many variations, especially those in the areas of temperaturecontrol with various transformations having occurred, when following theprocess of the present invention. Temperature control is an importantaspect of this invention and its control is important to the formationof various partially and fully transformed Colascitic portions ofiron-based alloys.

INDUSTRIAL APPLICABILITY

This invention finds industrial applicability for making and using highstrength steel for automobile components, in the construction industry,transportation infrastructure, heavy construction equipment,anti-ballistics and armored products, ship building, and for consumerproducts.

What is claimed is:
 1. A method for rapidly micro-treating an iron-basedalloy to form at least one phase of a high strength alloy, said methodcomprising the steps of: providing an iron-based alloy having a firstmicro-structure with an austenite conversion temperature, said firstmicrostructure being capable of being transformed to an iron-based alloyhaving a second micro-structure; rapidly heating the iron-based alloy toa selected temperature above its austenite conversion temperature; andimmediately quenching at least a portion of the iron-based alloy in aquenching unit adjacent the heating unit to form at least one phase of ahigh strength alloy upon being rapidly heated to said selectedtemperature and then being rapidly quenched.
 2. The method of claim 1,wherein the resulting high strength iron-based alloy includes at leastone portion of a material including at least 55% of a secondmicrostructure selected from the group consisting of bainite, coalescedbainite, ferrite, martensite, pearlite, austenite, and Colascite.
 3. Themethod of claim 1, wherein the iron-based alloy is a low carbon steelwhich contains carbon in a range of between 0.001 percent carbon byweight (wt %) to 4 percent carbon by weight (wt %).
 4. The method ofclaim 1, wherein the iron-based alloy is in a form selected from thegroup consisting of wire, strips, sheets, any 2-dimensional continuouscross-section, 3-dimensionally variable workpieces, articles, hollowtubes and combinations thereof.
 5. The method of claim 1, furthercomprising an additional step of pre-heating the iron-based alloy to atemperature below the austenitic conversion temperature in a range ofabout 315° C. to about 705° C.
 6. The method of claim 1, wherein theheating is accomplished by a heating unit selected from the groupconsisting of gas torches, electric resistance heaters, fluidized beds,electric furnaces, plasma furnaces, microwave ovens, open environmentpropane forges, gas fired units, solid fuels, high temperature saltbaths, torches and any combination thereof.
 7. The method of claim 6,wherein the heating unit transfers heat by a way selected from the groupconsisting of radiation, conduction, convection, induction and anycombination thereof.
 8. The method of claim 1, wherein the rate ofheating is from 260° C./sec to 3000° C./sec.
 9. The method of claim 6,wherein the heating unit includes propane gas torch heads.
 10. Themethod of claim 1, wherein the selected temperature is at least betweenabout 723° C. to about 1450° C.
 11. The method of claim 1, wherein theselected temperature is at least between about 900° C. to about 1300° C.12. The method of claim 1, wherein the step of quenching the heatedalloy is accomplished by a quenching means selected from the groupconsisting of water, water-containing aqueous solutions, oil, moltensalt, brine solutions, gases including air, powders and any combinationthereof.
 13. The method of claim 1 in which quenching is accomplished ata rate of 315° C./sec to 6,000° C./sec.
 14. Apparatus for micro-treatinga low, medium, or high carbon iron-based alloy workpiece of a firstmicrostructure having an austenitic conversion temperature to form atleast one phase of a high strength alloy, comprising: a micro-heatingunit for rapidly heating at least a portion of the low carbon iron-basedalloy workpiece to a selected temperature, said micro-heating unit beingcapable of rapidly heating the workpiece to a temperature above theaustenitic conversion temperature; a quenching unit positioned adjacentthe micro-heating unit for rapidly quenching the heated iron-basedalloy; and a control unit for controlling and transporting theiron-based alloy workpiece through the micro-heating unit and thequenching unit during the rapid heating and rapid quenching to form atleast one phase of a high strength alloy upon being rapidly heated tosaid selected temperature and then being rapidly quenched.
 15. Theapparatus of claim 14, wherein the selected temperature is at leastbetween about 723° C. to about 1450° C.
 16. The apparatus of claim 14,wherein the heating unit is selected from the group consisting ofelectric resistance heaters, fluidized beds, electric furnaces, plasmafurnaces, microwave ovens, open environment propane forges, gas firedunits, solid fuels, high temperature salt baths, torches and anycombination thereof.
 17. The apparatus of claim 14, wherein the heatingunit is selected from the group consisting of stationary heating heads,heated warm forms, heated sheet stamp dies, heated conventional dies,heated progressive dies, heated line dies, heated roll forming dies,heated four slide dies, heated hydroforming units, side-to-side movableheaters, hinged movable heaters, heated environment pressure form units,and combinations therefore.
 18. The apparatus of claim 14, wherein thequenching unit adapts a quenching means selected from the groupconsisting of water, water-containing aqueous solutions, oil, moltensalt, brine solutions, air, and powders.
 19. The apparatus of claim 14,wherein the heating unit includes propane torches having blaster nozzlesand a valve control operably connected to said blaster nozzles foreffecting heating control.
 20. The apparatus of claim 14, wherein thequenching unit includes a water bucket with water therein as a quenchingmedium to cool the low carbon iron-based alloy and a chiller connectedto the water bucket to keep the water at a suitable temperature.
 21. Theapparatus of claim 14, further comprising a heat resistant insulatorlocated between the heating unit and quenching unit to insulate theheating unit from the quenching unit and to straighten the moving lowcarbon iron-based alloy while it is being heated and quenched. 22.Apparatus for micro-treating an article made of a low, medium, or highcarbon iron-based alloy having an austenitic conversion temperature toform a high strength steel article, comprising: a movable head heatingunit having a rapid heating rate for heating the carbon iron-based alloyto a selected temperature below its; a quenching unit positionedadjacent the heating unit for rapidly quenching the heated low carboniron-based alloy; spaced first and second tensioning units positioned onopposite sides of said heating and quenching units for moving said lowcarbon iron-based alloy article through said heating and quenchingunits, and a computer control unit for controlling and adjusting thefeed rate of the first tensioning unit, the draw rate of the secondtensioning unit, the heating rate of the heating unit and the coolingrate of the quenching unit, whereby the low carbon iron-based alloy hasa varying thickness.
 23. The apparatus of claim 22, wherein the selectedtemperature is at least between about 1040° C. to about 1270° C.
 24. Theapparatus of claim 22, wherein the movable heating unit is selected fromthe group consisting of electric resistance heaters, fluidized beds,electric furnaces, plasma furnaces, microwave ovens, open environmentpropane forges, gas fired units, solid fuels, high temperature saltbaths, torches and any combination thereof.
 25. The apparatus of claim22, wherein the movable heating unit includes propane torches havingblaster nozzles and a valve control operably connected to said blasternozzles for effecting heating control.
 26. The apparatus of claim 22,wherein the quenching unit adapts a quenching means selected from thegroup consisting of water, water-containing aqueous solutions, oil,molten salt, brine solutions, air, and powders.
 27. The apparatus ofclaim 22, wherein the quenching unit includes a water bucket with watertherein as a quenching medium to cool the low carbon iron-based alloyand a chiller connected to the water bucket to keep the water bucket atsuitable temperature.
 28. The apparatus of claim 22, further comprisinga heat resistant insulator located between the heating and quenchingunits to insulate the heating unit from the quenching unit and tostraighten the moving strip steel while it is being heated and quenched.29. The apparatus of claim 22, wherein the first and second tensioningunits are selected from the group consisting of drawing rollers, drivecapstans, and elongation drives.
 30. Apparatus for micro-treating aniron-based alloy workpiece having an austenitic conversion temperature,comprising: a set of gas fired torches having a heating rate of 420° C.to 4,000° C. per second for heating the iron-based alloy workpiece to afirst selected temperature above the austenitic conversion temperature;a water cooling unit connected to a chiller to maintain an ambienttemperature water, said unit being positioned adjacent the gas firedtorches for rapidly quenching the heated iron-based alloy; spaced firstand second set of tensioning rollers positioned on opposite sides of thegas fired torches and the water bucket for moving said heated iron-basedalloy workpiece through the gas fired torches and the water bucket, aheat resistant insulator located between the gas fired torches and thewater bucket to insulate the heating unit from the quenching unit and tostraighten the moving the iron-based alloy workpiece while heated andquenched; and a control unit for controlling the heating rate of the gasfired torch and the cooling rate of the water bucket, whereby theiron-based alloy forms into high strength steel.
 31. The apparatus ofclaim 30, wherein the first selected temperature is at least betweenabout 1040° C. to about 1270° C.
 32. The apparatus of claim 30, whereinthe set of gas fired torches including propane torches have blasternozzles and a valve control operably connected to said blaster nozzlesfor effecting heating control.
 33. The apparatus of claim 30, whereinthe water cooling unit includes a water bucket with water therein toquench the heated iron-based alloy and a water holding reservoir tocollect additional water from the water bucket.
 34. The apparatus ofclaim 30, wherein the first and second set of tensioning rollers arehydraulic pressure powered.
 35. The apparatus of claim 30, wherein theheat resistant insulator includes a ceramic plate and a carbon sheetwrapping around the ceramic plate.
 36. The apparatus of claim 30,wherein the control unit is computer controlled.
 37. A method of makinga single layer automobile panel, comprising: providing a micro-treatedintegral single layer steel sheet with bainite formed in a portionthereof, and the sheet being made of varying thicknesses by heating upto a selected temperature and immediately quenching under varioustension; and stamping the steel sheet to form a door panel having afront pillar and a rear pillar, whereby the front pillar and rear pillarof the automobile panel includes sufficient bainite formed therein toincrease strength and formability of the front and rear pillars.
 38. Themethod of claim 37, wherein the selected temperature is at least betweenabout 1040° C. to about 1270° C.